Esters



- PatentedSept. 22, 1931 UNITED STATES PATENT OFFICE BENJ 'AMIN T.BROOKS, OF GREENWICH, CONNECTICUT, ANT!) EUGENE J. CARD OF NEWARK, NEWJERSEY, ASSIGNORS T0 PETROLEUM CHEMICAL CORPORATION,

A. CORPORATION or DELAWARE ESTERS No Drawing.

This invention relates specifically to the dibutyl ester of A 4cyclohexene 12 dicarboxylic acid, and will be fully understood from thefollowing description. We may employ the said acid either in a form ofthe acid or its anhydride, and both such forms will be denotedgenerically in this specification and claims by the phrase A 4cyclohexene 1.2 dicarboxylic acid. The said acid may be made bycombining maleic acid or the anhydride thereof with butadiene. For thispurpose the butadiene and maleic acid or anhydride are mixed andpreferabl heated to temperatures of from 95 to 120 The reactants arepreferably present in substantially equimolar proportions and areretained under sufiicient pressure during the reaction period to holdthe butadiene in liquid phase. We may alternatively mix the maleic acidor its anhydride with hydrocarbon mixtures containing butadiene, or wemay add a solvent, such as benzol, to the reaction mixture.

In one procedure we may, for example, take the products of extensivecracking of petroleum oil as, for example, products of liquid phasecracking carried out at high temperatures say above 950 F. or in vaporphase at any pressure, and preferably separate therefrom a fraction theolefine content of which consists predominantlyof olefines of 4 carbonatoms to the molecule. Such a fraction prepared for example from theproducts of vapor phase cracking carried out at atmospheric pressure andtemperatures between 1050and 1150 F. may contain between 10 and 30% ofbutadiene. We preferably, however, separate the butadiene from such afraction by the process described in co-pend-,

ing application Serial No. 433,426, and after separation ofsubstantially pure butadiene therefrom admix said butadiene with maleicacid or its anhydride, thereby forming A 4 cyclohexene dicarboxylic acidanhydride. The dibutyl esters of this acid may be made by warming saidacid or anhydride with butyl alcohol preferably in the presence of acatalyst such as, for example, a catalyst which in the ordinary organicreactions facilitates the splitting on of water. One convenient methodof carrying out the re- Application filed June 16,

1930. Serial No. 461,642;

removed from the reaction zone thereby facilitating the process.

An alternative procedure consists in adding a small quantity, say not inexcess of 20% by weight, of benzol to the liquid reactants and thenheatin the ternary system so formed. to the boi ing point. The vaporsare then condensed and Stratified and the benzol alcohol layer isreturned to the still. This system also permits withdrawing of anyexcess of water from the reaction zone and facilitates the progress ofthe reaction.

When, the dibutyl ester of the normal alcohol is desired, normal butylalcohol is heated with the said acid, and in this case up to about 5% byweight of sulphuric acid may be employed as a catalyst. The said mixturemay be heated u to the boiling pointof the alcohol present fbr a periodof hours, and at the expiration of this time the excess of alcoholtogether with any water formed may be distilled ofi'. We find itconvenient to work with slightl more than 2 mols of alcohol for each mol0 acid, although the materials may, if desired, be mixed in anyproportions and the excess of either component may be separated at theconclusion of the reaction.

After distilling off the excess of alcohol and water, the crude ester isneutralized, for

example, with sodium carbonate, to neutralize any sulphuric acidpresent, and the pure ester may be separated by vacuum distillation.' Wehave found that the normal dibutyl ester boils at about 186 to 192 C.under 18 min. of mercury pressure.

The secondary dib'utyl ester may be made by substantially identicalprocedure except that in thisv 'case it is desirable to employ a smallerquantity of the sulphuric acid catalyst. About 2% by weight of 80%, H SOcontent, is preferred when forming the secondary dibutyl ester. We havefound that I the secondary dibutyl ester boils at 176 to 178 C. at-19mm. of mercur pressure.

Both of the hereinabove escribed esters are colorless and practicallyodorless oily fluids. They are solvents for gums, resins, 1o nitrocellulose, cellulose acetate, etc. They may be employed in combinationwith other solvents in the formation of lacquers, practically thoselacquers comprising cellulose esters, and are particularl valuable ashigh boiling oint plasticizers or lacquer films.

The ore o1ng specific description is for purposes 0 illustration and notof limitation. It is therefore our intention that the invention belimited only by the appended 0 claims or their e uivalents in which wehave endeavored to clalm broadly all inherent novelt Ve claim: 1. Thedibutyl ester of A 4 cyclohexene dicarboxylic acid.

2. The secondary dibutyl ester of A 4 cyclohexene dicarboxylic acid.

3. The new compound corresponding substantially to the formulaon-om-cn-oooom.

o OH|O -cooo.m

4. A solvent mixture for cellulose esters comprising the dibutyl esterof A 4 cyclohexene dicarboxylic acid.

BENJAMIN T. BROOKS. EUGENE J. CARDARELLI.

